Half and Average Life
Trending Questions
A radioactive sample is undergoing decay. At any time , its activity is and at another time , the activity is . What is the average lifetime for the sample?
If 80% of a radioactive element undergoing decay is left over after a certain period of time t from the start, how many such periods should elapse from the start for the 50% of the element to be left over ?
4
6
5
3
The half - life of a radioactive element is 30 min. The time interval between the stages of 33.3% and 67.7% decay will be ?
60 min.
90 min.
30 min.
45 min.
A radioactive element having decay constant to be 2.31×10−3 per day is reduced to 25% of its initial amount in a period of ?
300 days
600 days
150 days
450 days
- 1.2 hr
- 2.4 hr
- 8.2 hr
- 5.2 hr
- 2.9×10−10s−1
- 2.9×10−8s−1
- 2.9×10−6s−1
- 2.9×10−4s−1
- 2.9×10−10s−1
- 2.9×10−8s−1
- 2.9×10−6s−1
- 2.9×10−4s−1
A piece of wood was burned and 7.32 g of CO2 was collected. The total radioactivity in CO2 was 7.6 dpm. How old was the wood sample ? Given t12 of C - 14 = 5730 years, specific activity of carbon obtained from a fresh wood sample is 15.2 dpm.
5730 years
11460 years
22920 years
None of these
- 2.9×10−10s−1
- 2.9×10−8s−1
- 2.9×10−6s−1
- 2.9×10−4s−1
- 6.5×108 years
- 1.3×109 years
- 2.6×109 years
- 5.2×109 years
On analysis a sample of uranium ore was found to contain 0.277 g of 82Pb206 and 1.667 g of 92Si238. The half-life period of U238is4.51×109 years. If all the lead were assumed to have come from the decay of 92Si238, what is the age of earth?
5.20×103years.
1.14×109years.- 1.75×106years.
- 1.09×1010years.
Two radioactive element A and B have half - lives in the ratio of 1 : 2. If half - life A is 2 days, what will be the mole ratio of A to B after 12 days in a sample initially containing 1 mole of each ?
1 : 2
1 : 4
1 : 6
1 : 8
- 3.25 billion years
- 6.49 million years
- 3.25 million years
- 6.49 billion years
On analysis a sample of uranium ore was found to contain 0.277 g of 82Pb206 and 1.667 g of 92Si238. The half-life period of U238is4.51×109 years. If all the lead were assumed to have come from the decay of 92Si238, what is the age of earth?
5.20×103years.
1.14×109years.- 1.75×106years.
- 1.09×1010years.
A radioactive material decays by simulataneous emission of two particles with half - lives 1620 and 810 years. The time after which one - fourth of the material remains, is
1080 years
2430 years
3240 years
4860 years
A sample of uranium rock from moon contains equimolar amounts of U238 and Pb206. The age of the rock will be (t12for U238=4.5×109yrs)
4.5×109yrs.
9.0×109yrs.
13.5×109yrs.
2.25×109yrs.
The half - life of a radioactive element is 30 min. The time interval between the stages of 33.3% and 67.7% decay will be ?
60 min.
90 min.
30 min.
45 min.
- 7997.2
- 57, 570
- 11, 540
- 15140
The radioactive decay, 83Bi211→ 81Tl207, takes place in 10 L closed container at 0∘C. Half - life of 83Bi211 is 2.15 min. Starting with 1 mole of 83Bi211, the pressure developed in the container after 4.30 min. will be
16.8 atm
22.4 atm
2.24 atm
1.68 atm